Electromagnetic relay



March 15, 1938. o. LUHN 2,111,246

ELECTROMAGNET I C RELAY Filed Sept. 27, 1955 In van for:

. Patented Mar. 15, 1938 UNITED STATES PATENT OFFICE ELECTROMAGNETIC RELAY Oskar Liihn, Rodelheim, near Frankfort-on-the- Main, Germany Application September 27, 1935, Serial No. 42,407

3 Claims. (Cl. 175-420) Electric switches are known which are operis usual in coherers, to become a good electric ated by direct current obtained, for instance, from conductor, under the influence of weak pulsations a photo-electric cell on the illumination of the of current and to lose the developed conductivity latter and passing through a contact instrument under the influence of the smallest shock, for 5 constructed as a galvanometer. However, known instance, as produced in the present instance by devices have the defect that, on account of the the armature c. A good effect is obtained by arpoor contact made by the needle forming the ranging, between the two parts of the body of contact member, a reliable closing through the the resistance, a frame :1: of mica which slightly needle of the circuit of the not very sensitive reseparates electrically the two portions of tinsel lay cannotbe achieved. This defect of devices with which the U-shaped members are charged. 10 of this kind arises from the sparking which 00- The variable resistance has two functions to ours between the needle and the rigid contact perform, namely: to bring about a strong spark with which it co-operates, which sparking is all quenching at the contacts at the moment when the more noticeable when the contact of the current pulsations are produced by the contact 10 needle is weak. This sparking prevents a reof the needle I of a moving coil galvanometer l5 liable functioning of the device. The arrangewith either of two contacts g and g'-', and to ment, in parallel with the contact, of a capacity cause a direct current to flow which releases the adapted to obviate the sparking, helps matters relay. to some extent, but it tends to cause the contacts In order to break the circuit of the electroto stick, so that again a reliable functioning of magnet immediately after the switching opera- 20 the apparatus will not be obtained. tion, a contact spring h is provided which is con- The object of the present invention is to obtrolled by but insulated from the armature c and viate these drawbacks and to obtain an appawhich co-operates with a rigid contact 1', normalratus in which a contact instrument constructed ly closed and which is connected to the positive as a galvanometer with moving coil can be used pole of an electricsource K, the contact 1' being 2r with satisfactory results. connected to one end of the winding of the elec- The invention consists in the provision of a tro-magnet a. The other end of the winding is variable resistance of special construction which connected to the binding post e, through a wire is arranged in the circuit of an electro-magnet K, to a contact spring m, and also to a contact and an electric source and which normally pre- 1- with which the armature d co-operates. The 30 vents the magnet from being energized but which contact spring m is arranged to sweep a cam allows a partial energization thereof under the wheel a by means of which they are, according influence of weak pulsations of current, so as to to the position of the wheel, brought into contact close a main circuit for a complete operation of with contacts 0 and g which are electrically the switch, a contact maker, which may be operconnected to the contacts g and g of the moving 35 ated through the medium of a photo-electric cell coil p. The needle I of the moving coil is conor the like, being provided for setting up the renected through V and a wire K with the negative quired pulsations of current, and means being pole of the electric source which is also connected provided for causing said contact maker and to the armature d and through a wire K to the switch to co-operate for restoring the relay to armature c. 40 operative position. The cam wheel 8 is connected to a ratchet The relay is illustrated by way of example in wheel a and is rotated through one tooth space the accompanying drawing Fig. 1 of which repof the latter each time the armature c is restored resents a diagram of the electric connections, and to normal position after having been acted upon Fig. 2, a section of the variable resistance. by the magnet a, the armature being provided 45 The relay comprises an electro-magnet a, arwith a pawl 0 which acts on the ratchet wheel. matures d and c, and a variable resistance or By the rotation ofthe cam wheel. the contacts eoherer b which is mounted on the armature m and n are alternately changed over so as to cand which is composed of two U-shaped, pressed contact with one or the other of the contacts so members 12 and b of insulating material. The with which they co-operate. At each operation resistance contains two vibratory electrodes c of the cam wheel, the contact spring m causes the and c one of which is electrically connected to connection between the needle and the variable the armature c and the other to a binding post e. resistance, through one of the contacts 9 and The U-shaped members are moreover charged a, to be broken. A second contact spring 1: is with material, for instance tinsel 2 adapted, as provided which is controlled by the cam wheel and which co-operates with contacts r and r'. The latter may be utilised for actuating signals indicating that the device has been properly operand.

Iitheneedleloithecoilpshouldbemoved by a current irom a photo-electric cell s from thecontact a to the contact a, a-hardly perceptible sparking will be set up by means of which weak pulsations oi current are made to how through the normally open shunt circuit traced thromh K-i-coil oi a-fl-m-flg''l-V'K'K, and the conductivity of the resistancebwillthmbeincreasedsothatdirect current to the extent oi 30-50% oi the normal. will pass through the winding oi the electromagnet a.

The second. normally closed shunt circuit which is traced through K-i-coil oi o-e-bcK -K. will thus he energized by the excitationoithecohererresistance bthroughthegalvanometer. The relieving armature d oi the magnetwillthenbeoperatedandplacedagainst the contact I. whereupon the iull current will ilow through the main circuit traced through K-i-coll oi magnet cl-d-K. This enables the magnetatooperatethearmature cuntilthe circuit is broken at i by the liiting oi the spring it. Since in this operation the armature c strikes against the iron core oi the electro-magnet a, the compensation eiiect oi the variable ruistance b sets in at the moment the circuit is broken, the value of the resistance is restored substantially to normal. and the armature it will therefore be tutored to its initial position. The armature calsoreturnstoitslnitial positlonandinso doingturnsthecamwheelssosstochangethe positions oi the contact springs, i. e., the connection between. the resistance 0 and the contact against which the needle I bears, will be broken by the spring 1n, and the apparatus will be prepared ior renewed operation.

I claim:

1. An electro-magnetic relay ior operating switches and the like, comprising an electromgnet, a switch operating armature for said magnet; a normally open main circuit ior said magnet including a source oi direct current capable oi operating said armature. a normally closed shunt circuit ior said magnet. a variable resistance in said shunt circuit operative to prevent normally a iiow oi current through the magnetand to allow such how to a limited under the influence oi electric pulsations. a normally open second shunt circuit connected to said resistance, a contact maker in said second shunt circuit capable oi being operated by weak current ior setting up pulsations in the resistance causing a partial eneiglaation oi the magnet, means operated by the magnet under the iniiuence oi such partial energisatlon ior closing the, mainclrcuitandoperatingthearmature.aswitch operating element connected to said meansiorbreakingthemain circuitonthe arma-. ture being operated. and means controlled by the switch operating element ior restoring the relay to operative position.

2. A relay as claimed in claim 1 switch operating element comprises a rotary cam wheel and a pawl and ratchet mechanism ior rotatingsaidwheeLandwhereinthemeansiorrestoring the relay to operative position comprises aspringcontsctarrangsdtobesweptbysaidu camwheel.

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